Daniel Chalef

Daniel Chalef is founder and CEO of Zep, a San Francisco company from Y Combinator's Winter 2024 batch that builds context graphs so AI agents can recall users, accounts, and business data over time.

Returning to Founding a Second Time

He calls himself an engineer turned founder. Zep is his second startup and his second open-source startup, he told Kenn So of Generational in 2025. His first was KnowledgeTree, and he later worked as a late-stage operator at SparkPost, which was acquired by MessageBird, according to his Y Combinator profile. Between the two startups he led product-focused machine learning and engineering groups, marketing, and corporate development teams.

Open-Sourcing a Memory Tool

He had worked with language models since BERT and BART in 2017 and 2018. In early 2023 he set out to build an agent that could turn policy and process documents into working processes, and ran into the problem that models kept no state between calls. He built a tool that summarized conversations, open-sourced it, wrote LangChain connectors for it, and became a top 10 LangChain contributor. From there he went through Y Combinator and built Zep as a multi-tenant service.

Betting on Temporal Graphs

He told Generational that vector databases could not capture how facts relate or change over time, so Zep combined graph and semantic search. Graphiti, the open-source framework behind it, uses keyword and semantic search to find the relevant part of a user's graph and then follows its connections to recent memories. His Y Combinator profile says he is still an engineer at heart with a soft spot for the Go language.